Thermal relay



R. T. PIERCE THERMAL RELAY March 19, 1929.

Filed Aug. 18, 1921 UV Ks,

INVENTQR Rag/florid THE/'68 ATTORNEY protected The mercury relay clinic-inn r, or wrnnrnsenne,

ZELEKHFRIG tit WUFAGTURENG @QllrLPrh lY, A @GRPEDRATIQN return.

Application filed August 18, 1921.

My invention relates to relays and particu larly to thermal relays.

Une object of my invention is to provide a thermal relay that shall protect an electric circuit in accordance with the temperature obtaining within a predetermined portion of the circuit. v I

Another object of my invention is to provide a relay, ofthe ehove indicated character, wherehy an auxiliary control circuit shall be controlled and energized in accordance With the temperature of a predetermined portion of the circuit. v

A further object of my invention is to pro vide a relay, of the shove-indicated character, that embodies a fluid conduct-orto be heated in accordance with a predetermined portion of the circuit serving to control the auxliary control circuit in accordance with the temperature of that portion,

A further object of my invention is to provide n relay out the shove-indicated character that shall be simple and economical in conctniction and efiec'tire and reliable in its oporation,

In any co igending application, Serial No, ll-933%, filed Aug. 18, 19121, I disclose a directtrip system wherein a thermal relay of the mercury type is employed to control the energizetion oi the trig) coil from the circuit to he illustrated therein comprises a capillary tube containing a of mercury that is so connected to the circuit as to be heated in accordance with the temperature of the apparatus therein.

pen attaining a predetermined temperature, "the mercury column is broken or separated.

in prccticing any present invention, I pro- "ride a relay that operates upon he same princi cle. The relay comprises a tubular container of insulating material within which is disposed a column of mercury. Terminal inernhers are sealed into the tube at the respective ends thereof serve connecting means whereby the column of mercury may heconnected to an electric circuit The relay is designed to have temperature characteristic corresponding that or e predetermined portion of the circuit end, when a predeterruined temperature is attained-therein, engagement is efifected between the column or mercury and an auxiliary terminal member that normally engaged thereby, to co" plots a control circuit which is connected to IA, ASEIGNQR Tl) "WESTING- (OF PENNSYL- rnnniusn sonar.

such auxiliary completion of tion for the effected.

Figure l of the accompanying drawings is a diagrammatic view of an electrical circuit including a relay embodying my invention, and Fig. 2 is a diagrammatic view of a circuit including a modified form of the relay that is illustrated in Fig. l, 1

in l, a translating device, such as a motor 1, receives energy from a supply circuit 2 through a circuit interrupter 3. -Efi"ective protection for the motor 1 is provided by means of a thermal relay 4 that is energized from the circuit through a current trans former 5. The thermal rela ei is designed to have a temperature characteristic corresponding directly to that oi the motor L When predetermined dangerous temper ture is attained in the motor and, consequently, in the thermal relay l, the relay sheets the actuation or the interrupter 3 by completing a circuit for energizing the trip coil 6 of the interrupter.

The relay at a tubular member 7 of insulating material, such as glass or quartz, Within which is disposed a body cl mercurv 8 and two terminal members i and 10 that art sealed into the tube to normally engage the body of mercury 8, The tubular member 7 is further provided with an auxiliary chamber 11 that communicates therewith and Within which is disposed a terminal member 12 that normally does not engace the mercury Within thechernher. The terminal member 12 is connected to one terminal oi the trio coil through a source 13 of directcurrent 'BlECtIOIHOiZl VQ force. A complementary terminal member 14 is'disgcosed Within the tube 7 intermediate terminal member, Upon the such circuit, the desired operaprctection of the apparatus is the terminal members?) and it) and is con When a spark is produced by the mercury heating to a predetermined degree and separating within the tube 7 the circuit of the trip coil will be completed between the aux-' iliary contact members 12 and 14 and the trip coil will be energized to actuate the interrupter 3 to disconnect the motor from the circuit 2. i

In Fig. 2 is illustrated a modified form of the relay shown in Fig. 1. In the relay that is illustrated in Fig. 2, the chamber 11 is disposed at one end of the tube 7 and only one auxiliary terminal member 12 is employed. Energy for the trip coil is derived from the circuit through a potential transformer 15.

When the temperature characteristics of the circuit are such that the relay l is caused to operate, the mercury 8 within the tube 7 will rise to efi'ect engagement between the contact members 9 and 12, whereupon the circuit of the trip coil 6 will be completed and the interrupter actuated to disconnect the motor from the circuit.

It will be observed that, in the system employing a direct-current control circuit, the

presence of mercury vapor and an arc is sufficient to complete the circuit of the trip coil, while, in the system employing an alternating-current control circuit, engagement of the contact members by the mercury is necessary.

Although I have illustrated preferred forms of relays embodying my invention, various modifications may be made therein within the spirit and scope of the invention, as set forth in the appended claim.

I claim as my invention A thermal relay comprising a column of electric-conducting liquid, electrodes in contact therewith 'ada ted to pass a current therethrough, means wliereby said column is rup-. tured responsive to an abnormal current value therein, an additional electrode normally out of contact with said liquid, and

means responsive to the rupture of said column for completing a circuit through said additional electrode.

In testimony whereof, I have hereunto subscribed my name this 8th day of August 1921.

RAYMOND T. PIERCE. 

